Important similarities exist between the neural mechanisms of facio-vocal activity in animals and significant aspects of the symptomatology and known neurobiology of Gilles de la Tourette's Syndrome. These similarities suggest that the neural mechanisms of facio-vocal activity in the cat may be a good animal model for the study of the etiology of the disease. The proposed studies seek to elucidate further the neural mechanisms if facio-vocal behavior in the cat with a view to a sharper definition of the model, and through it developing some new hypotheses on the causation of Tourette's Syndrome that may be testable in humans. The neuroanatomical areas involved in facio-vocal activity will be studied with the 14C-2-deoxyglucose method in conjunction with electrical stimulation of brain sites that elicit vocalization, in order to identify all brain areas i.e., motor pathways as well as sensory and other integrative centers, involved in the causation of facio-vocal behavior. Retrograde and anterograde tract-tracing methods will be employed at functionally identified vocalization sites to determine the afferent and efferent pathways between areas involved in facio-vocal activity. The neurochemical basis of transmission in these vocalization pathways will be examined by immunohistochemical analyses of chemically defined neuron systems within them, and as appraisal of the functional role of the chemical systems attempted through an assay of the changes in the biochemical composition of the cerebrospinal fluid during brain stimulation evoked vocalization and in cats with lesions that make them vocalize excessively. The role of the periaqueductal central gray in mediating facio-vocal behavior will also be studied. A quantitative and sequential analysis of the call-site stimulation evoked behavior and behavior of lesioned cats will be undertaken to further specify relationships between sensory and attentional processes and facio-vocal behavior.